An electrically powered four wheel vehicle typically includes a pair of side sill members extending horizontally in a fore and aft direction in a mutually parallel relationship, a pair of front side members connected to the front ends of the respective side sill members in a mutually parallel relationship, and a rear sub frame having a ladder or a cage structure connected to the rear ends of the side sill members. A pair of front wheels are supported by the front side members via respective strut suspension systems, and a pair of rear wheels are supported by the rear sub frame via respective strut or wishbone suspensions systems. A power unit including an electric motor is mounted on the rear sub frame. A front seat is positioned between the two side sill members, and a pair of rear seats are positioned on the rear sub frame. A battery unit for providing electric current to the electric motor is positioned under the front seat. See JP2014-94617A, for instance. JP2015-89806A discloses a slightly different electric four wheel vehicle.
In such a four wheel vehicle, the need for a rear sub frame causes the number of the structural component parts to be increased, and the frame structure to be highly complex. As a result, the production efficiency is impaired, and the weight of the vehicle body is undesirably great. In particular, in the case of a small electric vehicle known as MEV (micro electric vehicle) seating only one or two persons, there is a strong need to simplify the vehicle body structure for a desired production efficiency while ensuring an adequate mechanical strength. Furthermore, the weight of the vehicle body is required to be minimized so that the traveling range for a given battery capacity may be maximized.